We investigated the molecular effects of glucosamine supplements, a popular and safe alternative to nonsteroidal anti-inflammatory drugs, for decreasing pain, inflammation, and maintaining healthy joints. Numerous studies have reported an array of molecular effects after glucosamine treatment. We questioned whether the differences in the effects observed in previous studies were associated with the focus on a specific subproteome or with the use of specific cell lines or tissues. To address this question, global mass spectrometry-and transcription arraybased glucosamine drug profiling was performed on malignant cell lines from different stages of lymphocyte development. We combined global label-free MS-based protein quantitation with an open search for modifications to obtain the best possible proteome coverage. Our data were largely consistent with previous studies in a variety of cellular models. We mainly observed glucosamine induced O-GlcNAcylation/O-GalNAcylation (O-HexNAcylation); however, we also observed global and local changes in acetylation, methylation, and phosphorylation. (4,5). The clinical relevance of GlcN, a dietary supplement used in osteoarthritis patients, is unclear (6). Previous investigations of long-term GlcN administration did not reveal risks or concerns (7), which is also consistent with recent studies (8). However, in recent clinical studies, GlcN oral administration (8) did not demonstrate any benefits, and the concentration used in vitro was not comparable with the levels observed in the plasma in vivo after the oral administration of GlcN, which raised skepticism (8, 9). Therefore,